Question 1. Does the area for Class 1, Div. 1 and Div. 2 extend below grade within these
areas and if so how deep? My intrepretation is yes because of NEC 501.10(A)
(1) Exception. If the zone does not extend below grade then this exception
would not be needed.
Question 2. Can Schedule 40 PVC be used below grade under a Class 1, Div. 2 area? While
501.10(B)(7) requires Schedule 80 PVC in Div. 2 area, my interpretation is that
Table 300.5 (All Locations Not Specified below Row) applies allowing Schedule
40 Rigid PVC if it is at least 18" below grade.
Question 3. Can a seal off be installed in a conduit at the end of an underground conduit
just as it emerges above grade in an unclassified area (Class 1, Div. 2 to
unclassified boundary)? My interpretation is no because it is specifically
allowed by 501.15(A)(4) Exception #2 but this exception is not listed in
501.15(B)(2). I don't understand why this exception was not allowed in this
section since a seal is not even required if the conduit vents to atmosphere
outside in the unclassfied area.
Thanks for your help,
Rick Roof, P.E.
RWR Engineering
areas and if so how deep? My intrepretation is yes because of NEC 501.10(A)
(1) Exception. If the zone does not extend below grade then this exception
would not be needed.
Question 2. Can Schedule 40 PVC be used below grade under a Class 1, Div. 2 area? While
501.10(B)(7) requires Schedule 80 PVC in Div. 2 area, my interpretation is that
Table 300.5 (All Locations Not Specified below Row) applies allowing Schedule
40 Rigid PVC if it is at least 18" below grade.
Question 3. Can a seal off be installed in a conduit at the end of an underground conduit
just as it emerges above grade in an unclassified area (Class 1, Div. 2 to
unclassified boundary)? My interpretation is no because it is specifically
allowed by 501.15(A)(4) Exception #2 but this exception is not listed in
501.15(B)(2). I don't understand why this exception was not allowed in this
section since a seal is not even required if the conduit vents to atmosphere
outside in the unclassfied area.
Thanks for your help,
Rick Roof, P.E.
RWR Engineering